1. Field of the Invention
The present invention relates to a mechanical brake actuator providing an avoidance means to prevent a brake cable from disconnecting from a brake lever.
2. Description of the Related Art
This type of brake actuator has a mechanical actuating mechanism, which is comprised of a plate-like brake lever, a strut pivotally retained in the brake lever, and a pivotal pin, wherein the mechanical actuating mechanism is positioned between a pair of brake shoes, and the brake lever and the strut relatively rotates as operating, i.e., pulling and releasing a brake cable connected to the brake lever, also spreading the brake lever and the strut apart from each other.
Then, after a connecting pin that is penetrating through a cable connecting hole of the brake cable and a connecting hole of the brake lever, which is exposed from an opening of the strut as aligning both holes in series, thereby connecting the brake cable and the brake lever, an almost C-shape clip fits over an exterior of the strut, and recesses, which are formed on both internal side surfaces of the clip, engage with protrusions, which are formed on both external surfaces of the strut, for the clip to position the brake lever in a space between the facing plates of the strut. (See the paragraphs 0015-0016 and FIGS. 2-4 of the reference patent 1)
Furthermore, instead of the above-described structure, there exists an integral type where the clip is rotatably set on the strut. (See the paragraphs 0020-0023 and FIGS. 5-8 of the reference patent 1)
Also, for another means to position the brake lever in the space of the strut, a spring steel plate is bent to form a resilient member, which is to be set on the strut or the brake lever, where a resilient piece, formed on a part of the resilient member, is positioned along a rotational track of the brake lever, so as to restrict the rotation of the brake lever. (See the paragraphs 0018-0039 and FIGS. 2-12 of the reference patent 2)
The reference Patent 1 is the Japanese Provisional Patent Publication No. 2001-349360 (pages 4 and 5, FIGS. 2-8). The reference patent 2 is Japanese Provisional Patent Publication No. 2004-108458 (pages 5 and 9, FIGS. 2-12).
The invention disclosed in the reference patent 1 has the following problems.    (1) The clip needs to be wide so as to fit over the exterior of the strut; therefore, the material cost of the clip increases. Forming processes for fitting means on both clip and strut is necessary to prevent the clip from disengaging from the strut; therefore, the manufacturing cost is increased.    (2) If the clip is integrated with the strut, to provide rotational axis on both external surfaces of the facing plates is necessary, which increases the manufacturing cost.    (3) Both sides of the facing plates of the strut have notched grooves, which degrade the stiffness of the strut. Also, for a brake device which needs to lower the height, as the bridge portion of the strut is lowered, the notched groove becomes deeper, which degrades the stiffness of the strut.
The invention disclosed in the reference patent 2 has the following problems. (1) If the resilient member is inserted and set in a wide space of the strut, the space between the facing plates of the strut becomes larger. Therefore, this configuration gives a non-preferable layout, and it is difficult to apply in a small size brake device. If a brake device with a flexible layout choice is usable, which degrades the stiffness of the strut, the strut deforms easily. (2) If the resilient member is set on the bridge portion of the strut, the bridge portion needs to be smaller. Therefore, the facing plates, a constant space therebeween being maintained by the bridge portion, are more susceptible to an external force, thereby increasing the possibility of bending to open the same. (3) If the resilient member is set on the brake lever, which degrades the stiffness of the bridge portion.
The present invention was made in consideration of the above problems, and an object of the invention is to provide a mechanical brake actuator realizing the miniaturization of the entire device and the reduction of the parts costs. Furthermore, another object of the invention is to provide a mechanical brake actuator remarkably improving the clip setting operation.